added deep search of inheritance graph

test/constructor/no_pre_error.cpp

@@ -0,0 +1,19 @@
+
+// Test constructor cannot use `.precondition(...)`.
+
+#include <boost/contract/constructor.hpp>
+#include <boost/contract/guard.hpp>
+
+struct a {
+    a() {
+        boost::contract::guard c = boost::contract::constructor(this)
+            .precondition([] {}) // Error (must use constructor_precondition).
+        ;
+    }
+};
+
+int main() {
+    a aa;
+    return 0;
+}
+